This proposal will focus on the following three subjects: 1) Developmental changes in electrophysiological properties of Xenopus nerve and muscle cells in culture. 2) Synaptic interactions between mammalian clonal cell lines, and 3) Antibody against acetylcholine receptor as a probe for neurospecific interaction. Presynaptic and postsynaptic properties will be sytemmatically examined in Xenopus nerve-muscle cultures. Quantal nature of endplate potentials, spacial distribution of transmitter releasing sites along the length of nerve contact and susceptibility of presynaptic terminals against various treatments will be studied. Postsynaptically, properties of individual acetylcholine receptor (AChR) channels and electrical excitabilities are also planned to be studied. Effort to use clonal cell lines as a model for nerve-muscle interaction will be continued. A system in which both functional transmission and AChR accumulation occur will be searched. Monoclonal antibodies against AChRs will be used as a probe for nerve-muscle interaction. The effect of antibodies against various developmental steps will be examined. If recognition of AChRs were involved in some steps during development, the antibody may dissect out the molecular mechanism of the interaction.